NEW YORK — Every young ballplayer dreams about his major-league debut, conjuring up images in his mind how that monumental event will look and feel. All too often, though, reality douses fantasy, and debut performances sometimes are best forgotten.

So imagine the expression on Aaron Barrett's face yesterday afternoon, after the rookie reliever not only made his big-league debut on Opening Day, not only retired the side with a pair of strikeouts, not only did all this in the ninth inning of a tie ballgame in front of 42,442 fans at Citi Field and not only did all this with his parents, wife and other family members in attendance, but emerged from it all with his first career win to boot.

"I think I'm finally taking a deep breath and realizing that that happened today," he said about 30 minutes after the Nationals wrapped up their wild, 9-7, 10-inning victory. "It was everything I could've ever imagined for my debut. That was unbelievable."

That Barrett even found himself sitting in the Nationals' bullpen yesterday was surprising enough. The 26-year-old right-hander made the Opening Day despite no experience above Class AA Harrisburg (where he notched 26 saves last season) and a spring training locker located at the far end of the clubhouse at Space Coast Stadium, reserved for minor leaguers who have little-to-no chance of making the team.

Barrett, though, impressed club officials all spring with his performance (10 2/3 scoreless innings) and demeanor. And so he was given the final spot on the Opening Day bullpen roster.

Rookie relievers typically make their debuts in non-competitive situations, perhaps with their team getting blown out. Yet there was Barrett warming up in the top of the ninth yesterday alongside closer Rafael Soriano, told he would be entering if the game was tied heading into the bottom of the inning.

"The situation called for it," manager Matt Williams said. "He matched up well with the guys who were coming up, we thought. He's ready to pitch every day, so we got him out there. He did great."

Barrett admittedly had nerves as he trotted in from the bullpen.

"Either way, I was gonna be jacked up, regardless of what the score was," he said.

Upon reaching the mound, Barrett was surprised to see shortstop Ian Desmond waiting for him.

"Before I even start throwing my warm-up pitches, (he) just looked at me and said: 'Hey, just take a second and look around. Just take this all in,'" Barrett recalled. "I’m just really glad he did that, because I'll never forget that moment that he did that for me."

First baseman Adam LaRoche had a similar message for Barrett before he faced his first batter. Then it was down to business, and Barrett looked anything like a fresh young rookie. Showing complete confidence in his dominant slider, he struck out Omar Quintanilla, got Travis d'Arnaud to fly out to right, then struck out Ruben Tejada.

And when the Nationals rallied for four runs in the top of the 10th, Barrett found himself the pitcher of record, victorious on his very first day in the major leagues. He's the first pitcher in Expos/Nationals franchise history to win his big-league debut on Opening Day, only the third pitcher for any franchise to do it over the last decade.

Is it any wonder Barrett had the biggest smile of anybody in the Nationals' clubhouse late yesterday afternoon?

"Just to be in that situation ... tie ballgame, and in my debut I end up getting my first win," he said, shaking his head. "I mean, couldn't have chalked it up any better."